Bxobicel abqtjtmedes kojas



F. A. ROMS.

'RHEOSTAL AH'LlcArlon min Aun. 29.1911.

1,315,579. mendsepu 9,1919.

trated 'in irLoaIcnL Anomalies or maw Yonx, u. Y.

mueran Specification of Letters Intent.

Patented Sept. 9, 1919.

' Appieation med August 20, 1917. Serial No. 187,329.

To all whom :it may concern.'

Be it known that I, FLonIonL ARQUIMEDEB Rous, a 'citizen of the Republic of Santo Domingo residing at New York, in the countypf New Yorkand the State of New Yorkiiave invented a new and useful Rheo stat, of which the following is a specification.

My invention relates to improvements' in electric controlling devices in which the 'electric conductance of the specially arranged conductive and non-conductive substances is made to vary by compressing or expanding them between two bodies. This com ination of conductive rand non-conductive substances constitutes what will be called my resistance material, and will totally or partially take the place of the resistance coil of the ordinary rheostat.

The objects of my invention are, first, to provide a rheostat` so constructed that its resistance can be made to var consecutively from a very high degree o resistance down to the small fraction ofl an ohm; second, to afford facilities for increasing the .ampere carrying capacity of the rheostat; third, to provide means by which the temperature co-eliicient of the resistance material can be made a negli ble uantity; and, fourth, to afford means y which the resistance material can be so arranged as to have the value of its specific resistance Aand of its length and cross section suit the'electrical dimensions of the circuit which the rheostat is to control.

I attain these objects by mechanism illusthe accompanying drawings, in which Figure 1 is a vertical section through the rheostat on a plane corresponding to the plane of,the line 1--1,vr s s i Fig. 2 is a horizontal central section 'of a modified form of therheostat with parts broken away to show the interior construction and corresponding to the plane of line 2`2 of Fig. 1, and Y Fi 3 is a vertical central section ofxthis modi ed form of rheostat.

insulations, numerals 10 to insulating diaphragms, and numerals 8 theresisjtance material.

In Figs, 1, 2 and 3 the receptacle 3 constitutes the framewor of the rheostat and has a bottom 3* located therein', At the hub drawing apart of the fibers gr partie lposing the resistance material.

6 of the frame a threaded hole engages the screw 7; plates 9 yand 11 form the electrodes or terminals betweenV which the resistance material 8 is located, the plate 11 being electrically 'connected to the metallic spring 12 and insulated from the screw 7 yby means of insulation 4. The metallic springA 12 is insulatedy fromthe plate 9 by means of an annular diaphragm 10 and the spring 12 and plate 9 are Ialso insulated from the receptacle 3 by means of insulations 4.

The spring 12 is electrically connected to the binding post 15 by the screw shown in dotted lines in Fi 1 and constitutes therewith one termina ofthe rheostat, the other terminal being formed by connecting binding post 16 to plate 9 b means of a similar screw shown in a similiar manner in the same figure. These binding posts are insulated from the frame by means of insulating washers. p

The space inclosed by the plate 11 and plate 9 constitutes the receptacle for the resistance material.

By means of a suitable Stic material applied to the inner surfaces o these plates, those portions of the resistance material which come in contact with them are made to adhere to the plates, and when the plates are separated, the diaphragm 10 will serve as a stripper actin-g to help disarrange the close contact which the particles of tie resistance material assume under compression. A heavy oil and powdered the surfaces of the plates.

By loosening or tightening the screw`7 I do not intend to limit myself to the pre-f ferred example stated, but'may use any equivalent means for effecting a positive es com;

The wire coil resistance 2.4, shown in Figs- 1, 2 and 3, can be clrouited in paralgraphite may be l used as an adhesive material for covering W Vsus hile I have found the sticky material mentioned to ,be very effective in operation,

ldus

lel connection with the resistance material by means of contact plate 26 which is connected to binding post 15, as shown in dotted lines. By turning the screw 28 until s ring 27 is forced into contact with the p ate 26, the current maybe shunted through coil 24 and if desired any number of these coils of different resistance may be similarly connected to increase the conductibility of the rheostat.

The annular diaphragm shown in Fig. 2, is of a dili'erent construction from that shown in Fig. 1, in that the aperture 21 in Fig, 2 is of considerably smaller diameter and is concealed by the metallic plate 23, the purpose of this plate being to prevent the substance composing the resistance material, if of a powdered nature, from spilling out.

Fi a. 2 and 3 also illustrate an arrangement by which the length and cross section of the resistance material can be so arranged as to control a high voltage current wit in a com aratively small and limite space.

In gig. 2, 10 is an insulating diaphragm carrying the metallic plate 23 which seals the a erture 21. Th1-0u h this aperture 21, the p ate 23 comes into e ectric contact with the top layer of the resistance material, this top layer being insulated by means of the diaphragm sstance material which is shown throu h aperture 61 but both layers are electrica ly connected through this aperture 61. Another insulating ia hragm havin an aperture at 62 electrica ly insulates t e second layer from a third la er. of the resistance material. As many o these la ers and insulating diaphragme can be pied up electrically as is desired.' By havin the aper-` tures of the two succeeding laph s placed diametrically opposed to each ot er, the electric current can be forced to follow a tortuous' path and thus the pathcan beso lengthened as to be within the requisites of the given voltage and the eine of the aperture will enter into determining its ampere capacity. Y e plate '23 1f desired can be .removed and the, resistance material made to adhere directly to the plungerll and by operating the screw 7, the particles-ofthe resistance material of these layers can be forced together or d wn apart thus increasing or decreasing the conductivity of the layers and thus the dimensions of the electric current led to the binding posts 15 or 16 can be readily ad'usted to a given value.

The sti or adhA ive material may be applied to the terminal plates only or to b oth the terminal plates and the suv aces of the insulating diaphragme.

The resistance material 8 is made up of conductiveI and nl n-conductive substances associated 1n intimate mixtures of powders,

i 0B granules or laments'in a variety of ways from the second layer of ret tionof an ohmand will alford an and in accordance with the object Ain view. For instance, a non-conductive powder mixed with a conductive powdera conductive powder impregnating a bo y of' non-conuctive filaments', or a non-conductive fabric; two conductive powders, one having a positive and the other a negative temperature coeliicient either mixed with a nonconductive powder or im regnating a loose bod of non-conductive aments or fabrics.

xam les of these mixtures are as follows: First, asbestos powder and powdered graphite, second, granules of graphite or metal filings mixed with asbestos powder, powdered mica, glass or the owder of any refracto nonconductive su stance; third, powdere graphite and asbestos filaments or cotton fabric; and, fourth, gra hite in powdered or granular form pow ered German silver ,or manganin a loy with asbestos powder or iilaments.

It is a known fact that the conductance of graphite and other allotropc forms of carbon increases with the increase of temperature while the conductance of the metals decreases with the increase of temperature and therefore it is possible|to obtain, with a proper mixture of aphitel and a metallic powder, a compoun having a'zero temperature coellicient. 4 t j I am aware that prior to4 my invention rheostats have beenmade b l d upon" the principle of im erfectcontact between solid conductors, as, or' instance, pilesof graphite blocks intervening be ween two compressin bodies. Insuch dev ces, asudden rush 0I current of an appreciable' stren h takes place at the critical point where tact occurs.L Thisl differs altogether from the principal object of my invention, which is that of constructing arheostat whose resistance can be made to vary from the highest possible degree down to the smallest fracdesired de of, resistance between t ese two polnts., Such a variation lis not possible with carbon ment of solids but is accomplished by the composition of conductive and non-conductive substances of th e nature and arra substantially as set forth in the specification and drawin 1. In a rheostat, a eompressible resistance material and means' positively actin upon the material for drawing the materia apart to lessen its conductivity.

2. In a rheostat, a compressible resistance material havingA a zero temperature coeilicient and means for drawing the material apart to lessen its conductivity.

3. In a rheostat, a compressible resistance material and means,pos1tively acting uplon the material to lessen its density and t us deci-'ease its conductivity.

'piles or any other such arrange.

east coniso 4. In a rheostat,` resistance material including a multitude of particles of conductivematerial and means, positively acting upon the material for decree themutual contact between the said pat-,ic es to lessen the conductivity of the material as a whole.

' apart toA lessen its conductivity.,

7. In a rheostat, adjustable terminals, a compresslble resistance material between the terminals, means for causi the material to adhere to the terminals an means V:toracijusting the distance between the terminals to increase or decrease the conductivity ofthe resistance material.

8. In 'a rheostat, adjustable terminals, al` compresslble resistance material, having a zero temperature coelicient, between the termlnals, means .for causing the material to adhere to the terminals andmeans for adjusting the distance between the terminals to increase `or decrease the conductivity of i the lresistance material. l A

9. Ina rheostat,fadjustable terminals, .a compressible terminals, means for causing the material to 'adhere to the terminal adhere to the terminals and means for drawmg the terminals 4apart to lessen the conductivity of the resistance material. and means for forcing the terminals toward each other to increase the conductivity. Y

l10. In a rheostat, adjustab e terminal plates, a compressible resistance material between the p ates, adhesive means on lsaid terminal `plates for causing the material to lates and means for draw' the terminal p ates apart to' lessen the con uctivity of the resistance material Aeach other to increase its con LAplatesgil'ayers of compressi 4and staggered openins t e ce material Vbetvifeen the,

and for forcing the lates toward'each other to increase the co activity! il. In a rheostat, adjustable terminal plates, a shunt coil in the circuit, a compressible resistance material between the plates, meansfor drawing the plates apart to lessen the conductivity of the resistance material and strengthen the current in the shunt Vcoil and for-'forcing the glates toward uctivity and lessen the current in the shunt.

12. In a rheostat, -Mj,IlSialtleA terminal plates, a pluraiit of shunt coils inthe circuit, a compressi le resistance material between the plates, means forl drawing the plates apart to lessen the conductivity of the resistance material` and'strengthen the current inthe shunt coils and for forcing the plates toward each other ductivity and lessen thecurrent in the shunt.

"13. In a rheostat, adistable terminal y le resistance material between ythe Elates, diaphragms interposed etween the said ayers, means for causin the resistance material to adhere to the sai plates, means for varying the conductivity of the resistance. material in said -insulating diaphragms to cause current to travel a torzuous path through the resistance materia 14.. I1i a rheostat,j ad'ustable terminal plates, layers. of compressi le resistance material, between the plates, insulatin diaphragms interposed between the said ayers,

adhesive material on the surface of the insula diaphragme cause t e layers of resistance material to adhere to the said 'lates and diaphragme, means for forcingit e said-platestogether to increase the con nctivity of the resistance material and for draw1ng".the plates and consequently the material apart to decrease its condnctivity2 the said diaphrag'ms having staggered openings to cause the current to travelV a tortuous path through the resistance material. y

` rnoncnn ARQUIMEES ROJAS.

to increase-its con-V and terminal plates to f 

